The Ski-optometer should be equipped with two Maddox rods, one red and one white. Their combined use is of the utmost importance since they assist in accurately determining cyclophoria and its degree of tortion as designated on the degree scale, and fully described in a later chapter.
When the Maddox rods are placed in a vertical position, it is an indication that the vertical muscles are being tested; when placed horizontally, the horizontal muscles are being tested. It should be particularly noted that the streaks of light observable through the Maddox rods always appear at right angles to the position in which they lie.
The Ski-optometer should be placed in a comfortable position before the patient’s face with the brow-rest and pupillary distance adjusted to their respective requirements. The instrument should be levelled so that the bubble of the spirit level lies evenly between its two lines, thus insuring horizontal balance. The muscle test light should be employed at an approximate distance of twenty feet on a plane with the patient’s head. Best results in muscle testing are secured through the use of the Woolf ophthalmic bracket, with iris diaphragm chimney and a specially adapted concentrated filament electric lamp ([Fig. 9]). This gives a brilliant illumination which is particularly essential. The test for error of refraction should be made in the usual manner, using the spherical and cylindrical lenses contained in the Ski-optometer, thus obviating the transference of trial-case lenses and the use of a cumbersome trial-frame. The time-saving thus effected enables the refractionist to include a muscle test in every examination and without tiring the patient—a consideration of the utmost importance.
Binocular and Monocular Test
The test for muscular imbalance may be divided in two parts. First, binocular test, or combined muscle test of the two eyes; second, monocular test, or muscle test of each eye separately. The latter does not signify the shutting out of vision or closing off of either eye, since muscular imbalance can only be determined when both eyes are open. These two tests are fully explained in the following chapter.
Chapter VII
THE BINOCULAR MUSCLE TEST
Made with the Maddox Rod
and Phorometer
Directing the patient’s attention to the usual muscle testing spot of light, the red Maddox rod should be placed in operative position before the eye, with the single white line or indicator on red zero ([Fig. 15]). The rods now lie in a vertical position.
Fig. 15—The Maddox rods placed vertically denote test for right or left hyperphoria, causing a horizontal streak to be seen by patient.